function addToList() {
        var select_1=document.getElementById("productList");
        var select_2=document.getElementById("yourList");

        if (select_1.selectedIndex != -1) {
                var selectedOption=select_1.options[select_1.selectedIndex];
                if (selectedOption != null) {
                        var newOption=new Option(selectedOption.innerHTML,selectedOption.value,false,false);
                        select_2.options[select_2.length]=newOption;
                }
        }
}

function removeFromList() {
        var select_2=document.getElementById("yourList");

        if (select_2.selectedIndex != -1) {
                select_2.options[select_2.selectedIndex]=null;
        }
}

function truncateList() {
        var select_2=document.getElementById("yourList");

        while (select_2.length>0) {
                select_2.options[0]=null;
        }
}